1. Field of the Invention
This invention relates to input circuits for use in the selection of one of a number of inputs and in particular to such circuits in which substantially zero power is consumed when no input is selected.
Such circuits find many applications, for example, in ultrasonic transmitters for the remote control of television receivers and also in push-button telephone sets.
2. Description of Prior Art
Input circuits of the above kind are known in which one of n.times.m inputs may be selected, the circuit comprising a set of n terminals and a set of m terminals and the selection of an input being signified by the appearance of a predetermined potential, different from potentials at the other terminals, at a terminal of the first set and at a terminal of the second set. In such circuits n.times.m switch units are conventionally provided, each unit effectively comprising a double pole switch with its movable contacts both connected to the predetermined potential, one of its fixed contacts connected with a terminal of the first set, and its other fixed contact connected with a terminal of the second set such that no two switches are connected with same two terminals. Selection of a particular input may thus be achieved by operating one of the n.times.m switch units, thus applying the predetermined potential to a particular terminal of the first set and to a particular terminal of the second set.